STUDIES IN MAMMALIAN EMBRYOLOGI. 499 



Studies in Mammalian Embryology. 



II.— The Development of the Germinal Layers 

 of Sorex vulgaris. 



By 



A. A. ^W. Hubrecbt, lili.D., C.]tI.Z.S., 

 Professor of Zoology in the University of Utrecht. 



With Plates XXXVI— XLII. 



Introduction. 



Of all embryological problems those concerning the gastru- 

 lation process of the Amniota and the formation of their raeso- 

 blast and notochord may certainly be said to be at the present 

 moment one of the most burning questions ; not only because 

 of the number of important investigations that have of late 

 years been directed towards their solution, nor of the high 

 authority of the names of many of those who have been en- 

 gaged in these investigations, but more especially because of 

 the very conflicting results and conclusions to which these 

 different researches have conducted their authors. 



If I venture to add new fuel to this fire it is only because 

 I am not without hopes that the manner in which the facts 

 present themselves in the as yet uninvestigated species of 

 primitive Mammalia (Insectivora) which have been the object 

 of my own researches may serve to reconcile varied and oppo- 

 site interpretations to which the rabbit (Kolliker, van Beueden, 

 Rabl, a. o.), the guinea-pig (Carius, Keibel, Strahl), the cat 

 (Fleischmaun), the opossum (Selenka), the bat (van Bene- 

 den), the mole (Lieberkiihn, Heape), and the sheep (Bonnet) 

 have led those respective authors. 



VOL. XXXI, FART IV. — NEW SER. L L 



